Dropbox is a Web-based file hosting service operated by Dropbox, Inc. that uses networked storage to enable users to store and share files and folders with others across the Internet using file synchronization. It was founded in 2007 by MIT graduates Drew Houston and Arash Ferdowsi as a Y Combinator startup.

There are both free and paid services, each with varying options. Dropbox offers a relatively large number of user clients across a variety of desktop and mobile operating systems. There are a number of versions across many operating systems, including versions for Microsoft Windows, Mac OS X, and Linux (official and unofficial), as well as versions for mobile devices, such as Android, iPhone, iPad, WebOS, and BlackBerry, and a web-based client for when no local client is installed. Dropbox uses the freemium financial model and its free service provides up to 18 GB of free online storage (2 GB + 512 MB per referral).